John thomlinson



drive off water from it.

UNITED STATES PATENT OFFICE.

JOHN THOMLINSON, OF KNOTHILL WORKS, CARLISLE, ENGLAND.

PLASTER- OR CEMENT.

SPECIFICATION fannin part of Letters Patent No. 834,489, dated January 19, 1886.

Application filed July 27, 1885.

For this purpose I take plaster-stone or sul phate of lime, and by the usual processes I I then add an imported mineral known as tincal, and obtain an intimate mixture of the two in afinelypowdered state. I also incorporate with these materials a proportion ofpowdered alum. The

. ingredients are mixed togetherdry, and I prefer to conduct the manufacture as follows: I grind the calcined gypsum in the usual manner to a fine powder. I also in like manner and separately grind the tincal. I mix the two powders in the proportion of about forty or fifty pounds of tincal to the ton of calcined gypsum. The proportions may be varied. If the quantity of tincal employed be somewhat greater than is stated above, the cement will be hardened, and if less be used the cement will becomparatively soft. The mixture of the two powders is in their dry state and should be very complete. It should be mentioned that gypsum varies much in quality, and that to attain a uniform standard in respect to hardness varying proportions of tincal will have to be used.

Serial No. 172,793. (No specimens.) Patented in England February 9, 1885, No. 1.773.

In some cases I mix other materials as well as tincal with the calcined gypsum. Thus a good cement is obtained from the following materials: finely-powdered calcined gypsum, one ton; finely-powdered tincal, forty-five pounds; finely-powdered alum, dry, fifteen pounds. The cement thus made Icall Robinsons cement. ltis of a similar character to the cements known as Keens, Parian, and Martins cement, and is adapted for use in every way that these cements are used, and for the making of fireproof ceilings and for various other purposes.

The process which I have described is very economical as compared with processes heretofore employed in producing like cements, and Robiusons cement can consequently be delivered in the market at a price which admits of its being employed for purposes for which common lime-plaster is now employed.

Having now particularly described and ascertained the nature of my said invention, and in what manner the same is to be performed, I declare that what I claim is The hereinbeforedescribed cement, consisting of calcined and powdered gypsum and powdered tincal with or without powdered alum, mixed together dry and in about the proportions set forth.

JOHN THOMLINSON.

Witnesses:

THOMAS LAKE,

17 Gracechurchfltreet, London, E. C. W. P. WARREN,

l7 Gracechm'ch Street, London. 

